Hitherto, it has been known that a laminate article impregnated with a thermosetting synthetic resin is obtained by laminating a plurality of sheets of paper or cloth impregnated with a varnish of primary condensate of a thermosetting synthetic resin such as phenol resin, urea resin, melamine resin, quanamine resin or epoxy resin and after evaporating the solvent for the primary condensate, pressing the laminate while heating the laminate to promote the condensation of the resin in order to harden the resin. The thus obtained laminate article impregnated with a thermosetting synthetic resin has been put to practical uses as plates, pipes and rods for a fairly long time.
However, in consideration of the necessity of saving resources and energy, the demand for articles made of synthetic resin has been diversified, for instance, the demand for products with water-proofness, higher surface hardness, higher mechanical strength, better processability and lighter weight has recently been increased so that the higherto publicly known laminate articles impregnated with a thermosetting synthetic resin are not necessarily possible to fully satisfy such a demand. Besides, in order to prepare the hitherto publicly known laminate article it is necessary to impregnate a varnish comprising the primary condensate of the resin into the basic material and to bring the impregnated primary condensate into further condensation. Accordingly, it is necessary to control the reaction conditions of the condensation according to the kinds of the resin used for the purposes, and such a control becomes to be a demerit because of its complicatedness. In addition, there is an economical demerit that the thermosetting resin is relatively expensive.
In consideration of these situation, there has been a raised demand for the articles of laminate impregnated with a thermoplastic synthetic resin with better processability and lighter weight.
However, since the viscosity of a solution of a thermoplastic synthetic resin in a solvent is, different from that of a primary condensate of a thermosetting synthetic resin, higher in proportion to its concentration and the permeability of such a solution into the basic material such as sheets of paper or cloth is not favorable due to the poor wetting property of the solution to the paper or cloth, it has been deemed to be difficult to prepare laminate articles impregnated with a thermoplastic synthetic resin up to present.
In other words, it has been believed that any practically utilizable articles cannot be obtained from the laminate material obtained by merely impregnating a solution of a thermoplastic synthetic resin into the basic material and laminating the thus impregnated basic material, because such an article is apt to be subjected to delamination.
The present inventors, as a result of studying the ways of putting a laminate article impregnated with a thermoplastic synthetic resin into practical use, have obtained an information that contrary to the above-mentioned usual recognition, sufficiently practicizable articles are possibly furnished by selecting the viscosity of the solution, emulsion or suspension of thermoplastic synthetic resin, the adhered amount of the resin impregnated to the basic material and the processing conditions of shaping the laminate articles, and thus attained the present invention.